CT with consolidations with air bronchograms in legionnaires' disease

An air bronchogram is defined as a pattern of air-filled bronchi on a background of airless lung. CC-BY icon

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Consolidations

pulmonary consolidation A pulmonary consolidation is a region of normally compressible lung tissue that has filled with liquid instead of air. The condition is marked by induration (swelling or hardening of normally soft tissue) of a normally aerated lung. It is conside ...

s and infiltrates, air bronchograms are most commonly caused by

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...

pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is due t ...

(especially with alveolar edema). Other potential causes of consolidations or infiltrates with air bronchograms are: *

Pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is due t ...

* Non-obstructive

atelectasis Atelectasis is the collapse or closure of a lung resulting in reduced or absent gas exchange. It is usually unilateral, affecting part or all of one lung. It is a condition where the alveoli are deflated down to little or no volume, as distinct ...

* Severe

interstitial lung disease Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue and space around the alveoli (air sacs)) of the lungs. It concerns alveolar epithelium, pu ...

* Pulmonary infarct *

Pulmonary hemorrhage Pulmonary hemorrhage (or pulmonary haemorrhage) is an acute bleeding from the lung, from the upper respiratory tract and the trachea, and the pulmonary alveoli. When evident clinically, the condition is usually massive.

* Normal expiration

Lung nodules

For

lung nodule A lung nodule or pulmonary nodule is a relatively small focal density in the lung. A solitary pulmonary nodule (SPN) or coin lesion, is a mass in the lung smaller than three centimeters in diameter. A pulmonary micronodule has a diameter of less ...

s, air bronchograms used to be associated with infectious causes of consolidation and, therefore to be

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

. However, in the setting of a lung nodule, an air bronchogram is actually more frequent in malignant than in benign nodules. studied the tumour-bronchus relationship and described five types: * In “Type 1” the bronchial lumen is patent up to the tumour. * In “Type 2” the bronchus is contained in the tumor. These types are more common in malignant nodules. * A compressed and narrowed bronchus is defined as “Type 3”, and can occur in both benign and malignant nodules. * Narrowing of the proximal bronchial tree is described as “type 4” and is associated with malignancy. * “Type 5” is a bronchus compressed and flattened by the nodule with intact smooth wall. This type is mainly seen in benign nodules. Keeping in mind how a tumour with lepidic growth expands, it is not surprising that the air bronchogram in these tumours is smooth. In contradistinction, a desmoplastic response may cause irregularities of the bronchogram. When retraction of tumoural fibrosis occur, the air bronchogram can even become somewhat dilated. Although this sign can occur in all lung cancer cell types, it is more common in adenocarcinoma. Studies suggest the association of this sign with an activated

epidermal growth factor receptor The epidermal growth factor receptor (EGFR; ErbB-1; HER1 in humans) is a transmembrane protein that is a receptor for members of the epidermal growth factor family (EGF family) of extracellular protein ligands. The epidermal growth factor rece ...

(EGFR) mutation.

References

{{reflist Lung disorders